Butterfly-type valve assemblies are commonly utilized onboard aircraft to the control flow of highly pressurized fluids, such as bleed air. A butterfly valve assembly commonly includes a flowbody having a flow passage therethrough, a drive shaft rotatably suspended within the flowbody, and a valve plate disposed within the flow passage and mounted to the drive shaft. To provide a substantially uninterrupted sealing surface, the drive shaft may be angled with respect to the flow passage and with respect to a sealing member (e.g., a wiper seal) carried by the valve plate. Opposing ends of the suspended drive shaft are each received within a cylindrical recess or annulus provided within the flowbody, and a rolling element bearing is often disposed around each shaft end to facilitate rotation of the suspended drive shaft. The flowbody may also include various mounting features (e.g., flanges) to facilitate mounting to the aircraft ducting and to support a valve actuator, which engages an end portion drive shaft to provide controlled rotation of the valve plate during operation of the valve assembly.
As the pressure differentials across the butterfly valve plate increase, and as the dimensions of the valve plate increase, so too do the forces exerted on the valve plate by pressurized fluid within the flow passage. In the case of a butterfly valve assembly including an angled drive shaft, both radial and axial (thrust) forces are transferred through the drive shaft to the rolling element bearings. When conventional contact angle ball bearings are utilized to support an angled drive shaft subjected to high radial and axial (thrust) loading, undesirably high hertzian stress concentrations may occur within each ball bearing, which can result in excessive deformation and wear of the bearing's rolling elements and an overall reduction in the bearing's load-bearing capacity and operational lifespan. Dual bearing configurations, which pair one bearing dedicated to radial loads with a second, neighboring bearing dedicated to axial loads, can be employed to reduce the hertzian stresses within each bearing; however, the usage of two bearings to support a shaft end adds undesired bulk, weight, part count, and cost to the butterfly valve assembly. Combination bearings have also been developed that include two neighboring rows of rolling elements (e.g., a row of ball-type rolling elements and an adjacent row of rollers) separated by an annular guide flange. The row of ball-type rolling elements is typically intended to react to axial (thrust) loads, while the row of rollers is intended to react to the radial loads. However, due to limitations inherent in manufacturing processes, it is difficult to ensure precise alignment between the rotational centers of the neighboring rolling elements within the combination bearing. Movement of the ball-type rolling elements can thus become undesirably restricted during to rotation of the combination bearing due to internal misalignments, and the ball-type rolling elements may carry not only the axial (thrust) load, but also a substantial portion of the radial load. High concentrations of hertzian stress may thus occur within the ball-type rolling elements, again resulting in an undesired reduction in the bearing's load capacity and operational lifespan.
It would thus be desirable to provided embodiments of combination bearing that achieves improved load segregation between at least two rows of rolling elements to reduce the hertzian stress concentrations within the bearing and thereby improve the bearing's overall load capacity and operational lifespan. Ideally, embodiments of such a combination bearing would be relatively lightweight and compact and, consequently, well-suited for usage within valve assemblies utilized within avionic applications. Finally, it would further be desirable to provide embodiments of a valve assembly including such a combination bearing. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and the foregoing Background.